Yogurt-eating mice found to have larger testicles

Research suggests certain probiotic bacterium causes elderly mice to experience increased testosterone levels

Topics: Scientific American, Mice, testosterone, probiotics, Science, sexuality,

Yogurt-eating mice found to have larger testicles
This article was originally published by Scientific American.

Scientific AmericanI don’t think I’m alone in my prurient interest in research related to sex, since those posts tend to be wildly popular. At the same time, I try mostly to stick to my field of expertise while blogging, and the intersection between sex and the immune system doesn’t happen that often (unless we’re talking about sexually transmitted infections). Even then, I’m writing for a food blog now, and the overlap in the sex/immunology/food venn diagram is even smaller. So when I read that mice eating yogurt had altered immune systems which led to increased testicle size, I almost couldn’t believe my luck!

Probiotic Microbes Sustain Youthful Serum Testosterone Levels and Testicular Size in Aging Mice (Open Access)

Actually, it’s not yogurt, but a particular bacterium often found in yogurt that causes the effects – mice fed Lactobacillus reuteri in their drinking water had larger testes than mice not given any probiotic. The results weren’t that huge (heh) – only 5% – but they used a lot of mice, and there’s not that much natural variation, so the result seems real. They also performed the important control of feeding mice a different bacterium (E. coli), and saw no difference.

That’s the testicle headline grabbing part of the story, but it’s only the beginning, and I actually found the rest of the paper more compelling. Normally, as mice (and people) age, testosterone production drops, largely because of the degeneration of a particular cell type called a “Leydig Cell,” that’s found in the testes. Decreased testosterone has been implicated in a number of the problems of aging in men (though based on a cursory review of the literature, it’s not clear to me if those studies are definitive), and some doctors have suggested hormone-replacement therapy in men that have particularly low levels.

Interestingly, these researchers found that mice given the probiotic bacterium maintained their testosterone production at pretty substantial levels into old age (which is 5 months for a lab mouse), and this was correlated with increased numbers of healthy Leydig cells, where their untreated partners’s Leydig cells atrophied. But how could a bacterium fed to mice in their drinking water decrease aging of the testes? Here’s where the immune system comes in (and for the record, this is yet another example of my mantra, the immune system is involved in every aspect of health).

This lab is really an obesity lab, and their previous studies have shown that certain probiotics can reduce the health problems associated with obesity by decreasing the production of a cytokine – a chemical messenger of the immune system – called IL-17. Normally, IL-17 is produced during an inflammatory response to deal with bacterial infections, but over production can cause tissue damage and is associated with a bunch of autoimmune disorders. The link between obesity and inflammation, has been well established, and this lab’s work has shown that probiotics can help with that.

They wondered if IL-17 might play a role in their gonad findings, and sure enough, blocking IL-17 with an antibody mimicked all of the effects seen with the probiotic. Which is cool, but ultimately unsatisfying. They don’t show that inflammation is involved in the atrophy of Leydig cells or do any experiments to establish the mechanism. I want to know why older mice are making IL-17 that’s killing their testes, and how these bacteria are stopping it.

More Related Stories

Featured Slide Shows

  • Share on Twitter
  • Share on Facebook
  • 1 of 11
  • Close
  • Fullscreen
  • Thumbnails
    Burger King Japan

    2014's fast food atrocities

    Burger King's black cheeseburger: Made with squid ink and bamboo charcoal, arguably a symbol of meat's destructive effect on the planet. Only available in Japan.

    Elite Daily/Twitter

    2014's fast food atrocities

    McDonald's Black Burger: Because the laws of competition say that once Burger King introduces a black cheeseburger, it's only a matter of time before McDonald's follows suit. You still don't have to eat it.


    2014's fast food atrocities

    Domino's Specialty Chicken: It's like regular pizza, except instead of a crust, there's fried chicken. The company's marketing officer calls it "one of the most creative, innovative menu items we have ever had” -- brain power put to good use.


    2014's fast food atrocities

    Arby's Meat Mountain: The viral off-menu product containing eight different types of meat that, on second read, was probably engineered by Arby's all along. Horrific, regardless.


    2014's fast food atrocities

    KFC'S ZINGER DOUBLE DOWN KING: A sandwich made by adding a burger patty to the infamous chicken-instead-of-buns creation can only be described using all caps. NO BUN ALL MEAT. Only available in South Korea.

    Taco Bell

    2014's fast food atrocities

    Taco Bell's Waffle Taco: It took two years for Taco Bell to develop this waffle folded in the shape of a taco, the stand-out star of its new breakfast menu.

    Michele Parente/Twitter

    2014's fast food atrocities

    Krispy Kreme Triple Cheeseburger: Only attendees at the San Diego County Fair were given the opportunity to taste the official version of this donut-hamburger-heart attack combo. The rest of America has reasonable odds of not dropping dead tomorrow.

    Taco Bell

    2014's fast food atrocities

    Taco Bell's Quesarito: A burrito wrapped in a quesadilla inside an enigma. Quarantined to one store in Oklahoma City.


    2014's fast food atrocities

    Boston Pizza's Pizza Cake: The people's choice winner of a Canadian pizza chain's contest whose real aim, we'd imagine, is to prove that there's no such thing as "too far." Currently in development.


    2014's fast food atrocities

    7-Eleven's Doritos Loaded: "For something decadent and artificial by design," wrote one impassioned reviewer, "it only tasted of the latter."

  • Recent Slide Shows


Loading Comments...